1. Field of the Invention
The present invention relates to the field of air treatment and conditioning apparatus and in particular, relates to exhaust hoods employed over cooking surfaces.
2. Description of the Prior Art
Commercial cooking, washing, and other food preparation stations typically require some means for removal of smoke, grease, vapors or steam which tend to accumulate over the station. Accumulations of such gaseous matter and airborne particulate matter have been removed by prior art apparatus which were as simple as an exhaust duct coupled to a collecting canopy or as sophisticated as an exhaust hood with provisions for make-up air drawn from the environment, directed by appropriate means to an exhaust inlet port and discharged through an exhaust duct back to the environment. In such latter cases, smoke and vapors would rise by natural convection and become entrained in the flow of make up air between the supply plenum and the exhaust duct. However, more than merely the smoke and vapor rising from the heated surface would be entrained within the make-up air flow. Considerable amounts of air would be drawn from the surrounding spaces, entrained in the make-up air flow and discharged to the environment. As a result, it is characteristic of such prior art exhaust hoods that significant amounts of air would be taken from the conditioned space, lost to the environment and would have to be replaced by the overall air treatment and conditioning facilities in the structure. The energy used to heat, cool or condition the air would thus necessarily be sacrificed in order to obtain the proper evacuation over the cooking or washing station. The greater the amount of steam and vapors which would have to be removed, the greater would be the quantities of make-up air required to be circulated through the exhaust hood during a given interval. The greater the amount of make-up air circulated through the exhaust hood, the greater amount of space conditioned air which would also be entrained within the air flow. Thus, the amount of energy lost to the environment also increased.
What is needed then, is a design for an exhaust hood which can provide the necessary capacity to evacuate the hood and yet minimize the amount of space conditioned air surrounding the hood which is removed from the space and lost to the environment.